Surface mount electronic component

ABSTRACT

A surface mount electronic component includes an element including a dielectric layer that includes a first main surface and a second main surface, a first external electrode disposed on the first main surface, a second external electrode disposed on the second main surface, a first metal terminal connected to the first external electrode by solder, a second metal terminal connected to the second external electrode by the solder, and an exterior material covering at least a portion of the element, the first and second external electrodes, and the first and second metal terminals. The solder satisfies a relational expression: element diameter D (mm)×about 0.003 mm≤solder cross-sectional area S (mm2)≤element diameter D (mm)×about 0.02 mm.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to Japanese PatentApplication No. 2017-035475 filed on Feb. 27, 2017. The entire contentsof this application are hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a surface mount electronic component.

2. Description of the Related Art

For example, as an electronic component including an electroniccomponent main body that is molded with a resin, the electroniccomponents described in Japanese Patent Application Laid-Open Nos.S59-210632, 2011-9431, and 2007-81250 have been disclosed.

Japanese Patent Application Laid-Open No. S59-210632 discloses anelectronic component which is connected to an electrode portion of aflat plate-shaped element having two electrode surfaces by soldering orthe like and in which a protective coating material is coated thereon.

Further, Japanese Patent Application Laid-Open No. 2011-9431 disclosesan electronic component in which lead-shaped metal terminals areconnected to both sides of an electronic component element, a coveringmember that covers the electronic component element is provided, and thelowest point of a mounting portion of the metal terminal and the lowestpoint of the covering member are arranged substantially in the sameplane.

Furthermore, Japanese Patent Application Laid-Open No. 2007-81250discloses a radial lead type electronic component including an elementportion coated with an insulating resin and two lead portions connectedto the element portion and a surface mount electronic componentincluding a case that internally accommodates the radial lead typeelectronic component.

However, in an electronic component as disclosed in Japanese PatentApplication Laid-Open No. S59-210632, when electronic components aremounted, they are mounted by flow mounting or welding with lead wiresinserted into a mounting board.

Accordingly, the electronic component cannot be mounted by reflowmounting in the first place.

Further, in an electronic component as disclosed in Japanese PatentApplication Laid-Open No. 2011-9431, although surface mounting ispossible, the flatness of a surface coated with a protective coatingmaterial is not sufficient. Thus, suction failure of a mounter of amounting machine used to mount an electronic component on a mountingboard occurs, the electronic component cannot be mounted on the mountingboard, and mounting failure may occur.

Furthermore, although Japanese Patent Application Laid-Open No.2007-81250 can solve the problem of Japanese Patent ApplicationLaid-Open No. 2011-9431, the radial lead type electronic component isaccommodated in the case, so that a problem occurs in which the heightof a surface mount electronic component increases. Thus, in recentyears, there are cases in which it is not possible to satisfy arequirement for miniaturization/height reduction of electroniccomponents due to height reduction of electronic equipment. Further,since a process for accommodating electronic components in a case isrequired, the production cost increases.

Furthermore, similar to Japanese Patent Application Laid-Open Nos.S59-210632, 2011-9431, and 2007-81250, in a case in which an amount ofsolder is not suitable to bond an element and a metal terminal, when anelectronic component is reflow-mounted, solder melts or expands to flowbetween a covering member (coating portion, coating material) and theelement, and thus to connect between opposing external electrodes,wherein short-circuiting may occur in some cases.

SUMMARY OF THE INVENTION

Preferred embodiments of the present invention provide surface mountelectronic components which enable reflow mounting to improvemountability and further reduce a height, and surface mount electroniccomponents which significantly reduce or prevent short-circuiting.

A surface mount electronic component according to a preferred embodimentof the present invention includes an element including a dielectriclayer that includes a first main surface and a second main surface, afirst external electrode disposed on the first main surface, a secondexternal electrode disposed on the second main surface, a first metalterminal connected to the first external electrode by solder, a secondmetal terminal connected to the second external electrode by the solder,and an exterior material covering at least a portion of the element, thefirst and second external electrodes, and the first and second metalterminals. In the surface mount electronic component, the first metalterminal includes a first bonding portion connected to the firstexternal electrode, a first extending portion connected to the firstbonding portion and extending in a direction parallel or substantiallyparallel to the first main surface with a space from the first mainsurface, a second extending portion connected to the first extendingportion and extending toward the element, a third extending portionconnected to the second extending portion and extending in the directionparallel or substantially parallel to the first main surface, a fourthextending portion connected to the third extending portion and extendingin a mounting direction, and a first mounting portion connected to thefourth extending portion and mounted on a mounting board. The secondmetal terminal includes a second bonding portion connected to the secondexternal electrode, a fifth extending portion connected to the secondbonding portion and extending in a direction parallel or substantiallyparallel to the second main surface with a space from the second mainsurface, a sixth extending portion connected to the fifth extendingportion and extending toward the element, a seventh extending portionconnected to the sixth extending portion and extending in the directionparallel or substantially parallel to the second main surface, an eighthextending portion connected to the seventh extending portion andextending in the mounting direction, and a second mounting portionconnected to the eighth extending portion and mounted on the mountingboard. The solder satisfies a following relational expression: elementdiameter D (mm)×about 0.003 mm≤solder cross-sectional area S(mm²)≤element diameter D (mm)×about 0.02 mm.

In a surface mount electronic component according to a preferredembodiment of the present invention, the solder is preferably alead-free solder having a high melting point.

In a surface mount electronic component according to a preferredembodiment of the present invention, preferably, upper and lowersurfaces of the exterior material are flat or substantially flat.Further preferably, in the first bonding portion, a distal end of thefirst bonding portion is disposed in a direction away from the firstmain surface from an intermediate portion of the first bonding portiontowards the distal end, and the first bonding portion is in surfacecontact with the first external electrode at the intermediate portionlocated on an opposite side of the distal end. Further preferably, afirst cut-out portion is provided in a portion in which the secondextending portion and the third extending portion of the first metalterminal intersect with each other. Further preferably, the secondbonding portion includes a bifurcated distal end and is in surfacecontact with the second external electrode at the bifurcated portion.Further preferably, a second cut-out portion is provided in the fifthextending portion of the second metal terminal. Further preferably, athird cut-out portion is provided in a portion in which the sixthextending portion and the seventh extending portion of the second metalterminal intersect with each other. Furthermore preferably, the first tothird cut-out portions are covered with the exterior material.

In a surface mount electronic component according to a preferredembodiment of the present invention, it is preferable that the firstexternal electrode and the second external electrode include a firstelectrode layer made of a Ni—Ti alloy and a second electrode layer madeof Cu.

In a surface mount electronic component according to a preferredembodiment of the present invention, the exterior material is preferablymade of a thermosetting epoxy resin.

In a surface mount electronic component according to a preferredembodiment of the present invention, it is preferable that the elementhas a disk shape, a diameter of an outer shape of this element is notless than about 3.4 mm and not more than about 5.0 mm, and a thicknessof this element is t=not less than about 0.90 mm and not more than about0.95 mm.

With a surface mount electronic component according to a preferredembodiment of the present invention, the element on which the firstexternal electrode and the second external electrode are arranged issupported not by a lead wire but by the first metal terminal and thesecond metal terminal and is able to be mounted on the mounting board bythe first metal terminal and the second metal terminal, and therefore,mounting by reflow is made possible.

With a surface mount electronic component according to a preferredembodiment of the present invention, the first metal terminal includesthe first bonding portion connected to the first external electrode, thefirst extending portion connected to the first bonding portion andextending in the direction parallel or substantially parallel to thefirst main surface with a space from the first main surface, the secondextending portion connected to the first extending portion and extendingtoward the element, the third extending portion connected to the secondextending portion and extending in the direction parallel orsubstantially parallel to the first main surface, the fourth extendingportion connected to the third extending portion and extending in themounting direction, and the first mounting portion connected to thefourth extending portion and mounted on the mounting board. In addition,the second metal terminal includes the second bonding portion connectedto the second external electrode, the fifth extending portion connectedto the second bonding portion and extending in the direction parallel orsubstantially parallel to the second main surface with a space from thesecond main surface, the sixth extending portion connected to the fifthextending portion and extending toward the element, the seventhextending portion connected to the sixth extending portion and extendingin the direction parallel or substantially parallel to the second mainsurface, the eighth extending portion connected to the seventh extendingportion and extending in the mounting direction, and the second mountingportion connected to the eighth extending portion and mounted on themounting board.

With the above-described configuration, a case member as disclosed inJapanese Patent Application Laid-Open No. 2007-81250 is not required,and the shape of the metal terminal is optimized, so that an increase inthe height dimension of the surface mount electronic component isprevented, and the height of the surface mount electronic component isable to be reduced.

With a surface mount electronic component according to a preferredembodiment of the present invention, the solder satisfies a followingrelational expression: element diameter D (mm)×about 0.003 mm≤soldercross-sectional area S (mm²)≤element diameter D (mm)×about 0.02 mm, andthis relational expression is satisfied with respect to both of thesolder bonding the first external electrode and the first metal terminaland the solder bonding the second external electrode and the secondmetal terminal. Accordingly, since a solder amount is set within anappropriate range, even if the solder melts or expands when the surfacemount electronic component is reflow-mounted on the mounting board,flowing of the solder between the covering member (coating portion,coating material) and the element is reduced or prevented while bondingis secured, so that short-circuiting is prevented.

With a surface mount electronic component according to a preferredembodiment of the present invention, when the solder is a lead-freesolder having a high melting point, while sufficient bonding strengthbetween the element and the metal terminal is provided, heat resistanceof the bonding portion to a flow or reflow temperature during mountingof the board is ensured.

With a surface mount electronic component according to a preferredembodiment of the present invention, if the upper and lower surfaces ofthe exterior material are flat or substantially flat, sufficientflatness is provided. Thus, it is possible to prevent suction failure ofa mounter of a mounting machine used to mount the surface mountelectronic component on the mounting board, and to reliably mount thesurface mount electronic component on the mounting board. As a result,the occurrence of mounting failure is prevented.

With a surface mount electronic component according to a preferredembodiment of the present invention, in the first bonding portion, thedistal end of the first bonding portion is disposed in the directionaway from the first main surface from the intermediate portion of thefirst bonding portion toward the distal end, and when the first bondingportion is in surface contact with the first external electrode at theintermediate portion located on the opposite side of the distal end, anamount of the solder that intrudes between the first bonding portion andthe first external electrode is increased. Therefore, the solder is ableto be sufficiently caught between the upper surface of the firstexternal electrode and the first bonding portion of the first metalterminal, and the bonding strength is increased.

In addition, the second bonding portion includes a bifurcated distalend, and when the second bonding portion is in surface contact with thesecond external electrode at the bifurcated portion, a contact areabetween the second metal terminal and the second external electrode isable to be increased, so that the element is stably supported with goodposture by the second external electrode, and the bonding strength isincreased.

With a surface mount electronic component according to a preferredembodiment of the present invention, when the first cut-out portion isprovided in the portion in which the second extending portion and thethird extending portion of the first metal terminal intersect with eachother, the second cut-out portion is provided in the fifth extendingportion of the second metal terminal, and the third cut-out portion isprovided in the portion in which the sixth extending portion and theseventh extending portion of the second metal terminal intersect witheach other, a flow path of the exterior material is secured when theexterior material is molded by injection molding, transfer molding, orthe like, and the filling property of the exterior material is improved,so that an effect of improving withstand voltage performance, moistureresistance reliability, and other advantageous characteristics areachieved.

With a surface mount electronic component according to a preferredembodiment of the present invention, when the first external electrodeand the second external electrode include the first electrode layer madeof a Ni—Ti alloy and the second electrode layer made of Cu, it ispossible to improve the bonding strength between the element and thesecond electrode layer by the first electrode layer in the firstexternal electrode and the second external electrode, and to improveelectroconductivity and ensure the bonding strength between the secondelectrode layer and the solder by the second electrode layer.

With a surface mount electronic component according to a preferredembodiment of the present invention, when the exterior material is athermosetting epoxy resin, adhesion between the exterior material andthe element or the metal terminal is ensured, and improved withstandvoltage and moisture resistance performance are obtained.

With a surface mount electronic component according to a preferredembodiment of the present invention, the element has a disk shape, andwhen the diameter of the outer shape of the element is not less thanabout 3.4 mm and not more than about 5.0 mm, and the thickness of theelement is t=not less than about 0.90 mm and not more than about 0.95mm, since the shape of the element is optimized, the size and height ofthe surface mount electronic component is reduced.

Preferred embodiments of the present invention provide surface mountelectronic components which allow reflow mounting to improvemountability and further reduce the height and surface mount electroniccomponents which reduce or prevent short-circuiting.

The above and other elements, features, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of the preferred embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an external perspective view showing an example of a surfacemount electronic component according to a preferred embodiment of thepresent invention.

FIG. 2 is a top view of the surface mount electronic component shown inFIG. 1 showing a surface mount electronic component according to apreferred embodiment of the present invention.

FIG. 3 is a side view of the surface mount electronic component shown inFIG. 1 showing a surface mount electronic component according to apreferred embodiment of the present invention.

FIG. 4 is a perspective illustration view showing an internal structureof a surface mount electronic component according to a preferredembodiment of the present invention.

FIG. 5 is a cross-sectional view taken along line V-V in FIG. 4 showinga surface mount electronic component according to a preferred embodimentof the present invention.

FIG. 6 is a top view of FIG. 4 showing a surface mount electroniccomponent according to a preferred embodiment of the present invention.

FIG. 7 is an external perspective view showing a state in which anexterior material is removed in a surface mount electronic componentaccording to a preferred embodiment of the present invention.

FIG. 8A is a side view of FIG. 7 showing the state in which the exteriormaterial is removed in a surface mount electronic component according toa preferred embodiment of the present invention, and FIG. 8B is anenlarged view of a bonding portion between a first bonding portion and afirst external electrode.

FIG. 9 is a perspective illustration view showing a state in which anelement is held by the first bonding portion of a first metal terminaland a second bonding portion of a second metal terminal in a surfacemount electronic component according to a preferred embodiment of thepresent invention.

FIG. 10A shows a state in which an element is held by a conventionalfirst metal terminal and a conventional second metal terminal, and FIG.10B shows a state showing a result when the element is held by theconventional first metal terminal and the conventional second metalterminal.

FIG. 11 is an enlarged view showing a second mounting portion of asecond metal terminal according to a preferred embodiment of the presentinvention.

FIG. 12 is a side view of a surface mount electronic component accordingto a preferred embodiment of the present invention and a view showing amounting state of the first mounting portion of the first metal terminaland the second mounting portion of the second metal terminal.

FIG. 13 is a cross-sectional schematic view of a surface mountelectronic component according to a preferred embodiment of the presentinvention and a view showing a relationship between a diameter D of anelement and a cross-sectional area S of a solder.

FIG. 14 is an explanatory view for explaining a method of measuring thecross-sectional area S of the solder.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of surface mount electronic components accordingto the present invention will be described. FIG. 1 is an externalperspective view showing an example of a surface mount electroniccomponent according to a preferred embodiment of the present invention.FIG. 2 is a top view of the surface mount electronic component shown inFIG. 1 showing a surface mount electronic component according to apreferred embodiment of the present invention. FIG. 3 is a side view ofthe surface mount electronic component shown in FIG. 1 showing a surfacemount electronic component according to a preferred embodiment of thepresent invention. FIG. 4 is a perspective illustration view showing aninternal structure of a surface mount electronic component according toa preferred embodiment of the present invention. FIG. 5 is across-sectional view taken along line V-V in FIG. 4 showing a surfacemount electronic component according to a preferred embodiment of thepresent invention. FIG. is a top view of FIG. 4 showing a surface mountelectronic component according to a preferred embodiment of the presentinvention. FIG. 7 is an external perspective view showing a state inwhich an exterior material is removed in a surface mount electroniccomponent according to a preferred embodiment of the present invention.FIG. 8A is a side view of FIG. 7 showing the state in which the exteriormaterial is removed in a surface mount electronic component according toa preferred embodiment of the present invention, and FIG. 8B is anenlarged view of a bonding portion between a first bonding portion and afirst external electrode.

A surface mount electronic component 10 according to a preferredembodiment of the present invention includes an element 12. The element12 is preferably a single ceramic plate and has a disk shape, forexample. The element 12 includes a first main surface 12 a and a secondmain surface 12 b facing each other and a side surface 12 c connectingthe first main surface 12 a and the second main surface 12 b.

The surface mount electronic component 10 further includes an externalelectrode 14 disposed on the first main surface 12 a and the second mainsurface 12 b of the element 12, a metal terminal 16 connected to theexternal electrode 14 with a solder 40 interposed therebetween, theelement 12, and an exterior material 18 covering at least a portion ofthe external electrode 14 and the metal terminal 16.

As a material of the ceramic plate, for example, a dielectric ceramicprimarily including BaTiO₃, CaTiO₃, SrTiO₃, CaZrO₃, or other suitabledielectric ceramic may preferably be used. Further, it is also possibleto use dielectric ceramics obtained by adding accessory components suchas a Mn compound, a Mg compound, a Si compound, a Co compound, and a Nicompound to these main components. In addition, piezoelectric ceramics,such as PZT-based ceramics, semiconductor ceramics, such as spinel typeceramics, and other suitable ceramics may also be used.

Since the element 12 is preferably made of a dielectric ceramic, theelement 12 functions as a capacitor. On the other hand, the element 12functions as a piezoelectric component when a piezoelectric ceramic isused, and functions as a thermistor when a semiconductor ceramic isused.

Although the outer diameter dimension of the element 12 is notparticularly limited, the diameter of the element 12 is preferably notless than about 3.0 mm and not more than about 6.0 mm, and morepreferably not less than about 3.4 mm and not more than about 5.0 mm,for example.

Although the thickness of the element 12 is not particularly limited, itis preferably not less than about 0.8 mm and not more than about 1.2 mm,and more preferably not less than about 0.9 mm and not more than about0.95 mm, for example.

The external electrode 14 is disposed on the first main surface 12 a andthe second main surface 12 b of the element 12.

The external electrode 14 includes a first external electrode 14 a and asecond external electrode 14 b.

The first external electrode 14 a is disposed on a surface of the firstmain surface 12 a of the element 12. The second external electrode 14 bis disposed on a surface of the second main surface 12 b of the element12.

Although the size of the first external electrode 14 a is notparticularly limited, it is preferable that the first external electrode14 a is disposed on the entire or substantially the entire first mainsurface 12 a of the element 12. Similarly, although the size of thesecond external electrode 14 b is not particularly limited, it ispreferable that the second external electrode 14 b is disposed on theentire or substantially the entire second main surface 12 b of theelement 12. This makes it possible to alleviate electric fieldconcentration as compared to a case in which a gap electrode isdisposed, and an effect of improving withstand voltage performance isobtained.

As the material of the external electrode 14, for example, a metal suchas Cu, Ni, Cr, Ag, Pd, Au, or Ti or an alloy containing at least one ofthese metals, such as Ag—Pd alloy, Cu—Ni alloy, Cu—Ti alloy, Ni—Cralloy, or Ni—Ti alloy, may preferably be used. The external electrode 14may be formed by laminating these metal materials.

In particular, the external electrode 14 preferably includes a firstelectrode layer (hereinafter referred to as Ni—Ti alloy layer) made of aNi—Ti alloy and a second electrode layer (hereinafter referred to as Culayer) disposed on a surface of the Ni—Ti alloy layer and made of Cu,for example.

In the external electrode 14, the Ni—Ti alloy layer and the Cu layer mayalternately be provided in a plurality of layers.

For example, the external electrode 14 of the surface mount electroniccomponent 10 may have a four-layer structure formed by alternatelyarranging the Ni—Ti alloy layers and the Cu layers. This makes itpossible to obtain the effect of improving the bonding strength betweenthe element 12 and the Cu layer as the second layer in the Ni—Ti alloylayer as the first layer. In the Cu layer as the second layer disposedon a surface of the Ni—Ti alloy layer as the first layer,electroconductivity is improved. In the Ni—Ti alloy layer as the thirdlayer disposed on a surface of the Cu layer as the second layer,diffusion of the solder 40 and an oxide layer to an underlying electrodeis reduced or prevented. In the Cu layer as the fourth layer disposed ona surface of the Ni—Ti alloy layer as the third layer, the bondingstrength with the solder 40 is improved.

The external electrode 14 is preferably formed by electroless plating,vacuum film formation, sputtering or other suitable method, for example.Although the thickness of the external electrode 14 is not particularlylimited, the thickness of the external electrode 14 is preferably notless than about 0.1 μm and not more than about 0.35 μm per layer, andthe thickness of the entire external electrode 14 is preferably not lessthan about 0.7 μm and not more than about 1.2 μm, for example.Consequently, the thickness of the external electrode 14 is able to bereduced, and the height of the surface mount electronic component 10 isable to be reduced.

The metal terminal 16 is connected to the external electrode 14. Themetal terminal 16 includes a first metal terminal 16 a and a secondmetal terminal 16 b.

The first metal terminal 16 a is connected to the first externalelectrode 14 a. The second metal terminal 16 b is connected to thesecond external electrode 14 b.

The metal terminal 16 is preferably a frame-shaped metal terminal, forexample. Since the metal terminal 16 is a plate-shaped lead frame, themetal terminal 16 thus defined by a plate-shaped lead frame allowsmounting on a mounting board, so that the surface mount electroniccomponent 10 is able to be mounted by reflow.

The metal terminal 16 includes a terminal body and a plating filmprovided on a surface of the terminal body.

The terminal body is preferably made of Ni, Fe, Cu, Ag, Cr, or an alloyprimarily including one or more of these metals, for example.Specifically, for example, the parent material of the terminal body maypreferably be Fe-18 Cr alloy, Fe-42 Ni alloy, or Cu-8 Sn alloy (Here,numerals before the atomic elements mean the amount in weight percent(wt %), and applies hereafter). The thickness of the terminal body ofthe metal terminal 16 is preferably not less than about 0.05 mm and notmore than about 0.5 mm, for example.

The plating film includes a lower layer plating film and an upper layerplating film. The lower layer plating film is provided on the surface ofthe terminal body, and the upper layer plating film is provided on asurface of the lower layer plating film. Each of the lower layer platingfilm and the upper layer plating film may include a plurality of platingfilms.

The lower layer plating film is made of Ni, Fe, Cu, Ag, Cr, or an alloyprimarily including one or more of these metals, for example. The lowerlayer plating film is preferably made of Ni, Fe, Cr, or an alloyprimarily including one or more of these metals, for example.

The upper layer plating film is made of Sn, Ag, Au, or an alloyprimarily including one or more of these metals, for example. The upperlayer plating film is preferably made of Sn or an alloy primarilyincluding Sn, for example. When the upper layer plating film is made ofSn or an alloy primarily including Sn, solderability between the metalterminal 16 and the external electrode 14 is improved.

The thickness of the lower layer plating film is preferably not lessthan about 0.2 μm and not more than about 5.0 μm, for example. Thethickness of the upper layer plating film is preferably not less thanabout 1.0 μm and not more than about 5.0 μm, for example.

When each of the terminal body and the lower layer plating film is madeof Ni, Fe or Cr having a high melting point, or an alloy primarilyincluding one or more of these metals, heat resistance of the externalelectrode 14 is improved.

The first metal terminal 16 a includes a first bonding portion 20 aconnected to the first external electrode 14 a, a first extendingportion 22 a connected to the first bonding portion 20 a and extendingin a direction parallel or substantially parallel to the first mainsurface 12 a with a space t1 from the first main surface 12 a, a secondextending portion 24 a connected to the first extending portion 22 a andextending toward the element 12, a third extending portion 26 aconnected to the second extending portion 24 a and extending in thedirection parallel or substantially parallel to the first main surface12 a, a fourth extending portion 28 a connected to the third extendingportion 26 a and extending in a mounting direction, and a first mountingportion 30 a connected to the fourth extending portion 28 a and mountedon the mounting board.

The second metal terminal 16 b includes a second bonding portion 20 bconnected to the second external electrode 14 b, a fifth extendingportion 22 b connected to the second bonding portion 20 b and extendingin a direction parallel or substantially parallel to the second mainsurface 12 b with a space t2 from the second main surface 12 b, a sixthextending portion 24 b connected to the fifth extending portion 22 b andextending toward the element 12, a seventh extending portion 26 bconnected to the sixth extending portion 24 b and extending in thedirection parallel substantially parallel to the second main surface 12b, an eighth extending portion 28 b connected to the seventh extendingportion 26 b and extending in the mounting direction, and a secondmounting portion 30 b connected to the eighth extending portion 28 b andmounted on the mounting board.

The first bonding portion 20 a of the first metal terminal 16 a is aportion connected to the first external electrode 14 a disposed on thesurface of the first main surface 12 a of the element 12. In the firstbonding portion 20 a of the first metal terminal 16 a, as shown in FIG.8, it is preferable that a distal end 20 a 2 of the first bondingportion 20 a is disposed in a direction away from the first main surface12 a from an intermediate portion 20 a 1 of the first bonding portion 20a towards the distal end 20 a 2. It is preferable that the intermediateportion 20 a 1 (that is, a portion located on the opposite side of thedistal end of the first bonding portion 20 a) of the first bondingportion 20 a is in surface contact with the first external electrode 14a. Consequently, an amount of the solder 40 that intrudes between thefirst bonding portion 20 a and the first external electrode 14 a isincreased. Therefore, the solder 40 is sufficiently disposed between theupper surface of the first external electrode 14 a and the first bondingportion 20 a of the first metal terminal 16 a, and the bonding strengthis increased.

Although the distal end of the first bonding portion 20 a is disposed ina direction away from the first main surface 12 a from the intermediateportion of the first bonding portion 20 a toward the distal end, anangle α between a direction connecting the intermediate portion of thefirst bonding portion 20 a and the distal end and the upper surface ofthe first external electrode 14 a is preferably an angle of not lessthan about 1° and not more than about 5°, for example. Within thisrange, the bonding strength between the first external electrode 14 aand the first metal terminal 16 a is ensured.

The width of the first bonding portion 20 a of the first metal terminal16 a is preferably not less than about 0.5 mm and not more than about0.9 mm, for example.

The second bonding portion 20 b of the second metal terminal 16 b is aportion connected to the second external electrode 14 b disposed on thesurface of the second main surface 12 b of the element 12. As shown inFIG. 9, the second bonding portion 20 b of the second metal terminal 16b preferably includes a bifurcated (for example, wrench-shaped) distalend, and it is preferable that the second bonding portion 20 b is insurface contact with the second external electrode 14 b at thebifurcated portion. That is, preferably a space 20 b 1 is provided at acentral portion of an end side opposite to a side connected to the fifthextending portion 22 b of the second metal terminal 16 b, provides apredetermined interval, and the second bonding portion 20 b is definedby one bonding piece 20 b 2 of the bifurcated shape and the otherbonding piece 20 b 3. Consequently, a contact area between the secondmetal terminal 16 b and the second external electrode 14 b is increased.Thus, the element 12 is stably supported with good posture by the secondexternal electrode 14 b, and the bonding strength is increased.

FIG. 10A shows a state in which an element is held by a conventionalfirst metal terminal and a conventional second metal terminal, and FIG.10B shows a result when the element is held by the conventional firstmetal terminal and the conventional second metal terminal. In a surfacemount electronic component shown in FIGS. 10A and 10B, first and secondexternal electrodes 2 a and 2 b are provided on both main surfaces of anelement 1, a first external electrode 2 a and a first metal terminal 3are connected to each other, and a second external electrode 2 b and asecond metal terminal 4 are connected to each other.

If the shape of the second bonding portion 20 b is not the bifurcatedshape (wrench shape) as in the present preferred embodiment but theconventional shape as shown in FIG. 10A, the center of gravity of theelement 1 cannot be supported vertically, so that the element 1 mayrotate. If the element 1 rotates, as shown in FIG. 10B, the element 1 isobliquely mounted with respect to a plane n parallel or substantiallyparallel to a mounting surface, so that there is a problem that amounting height of the surface mount electronic component is increased.

The bifurcated shape of the distal end of the second bonding portion 20b is not particularly limited to a wrench shape, and may be a U shape ora C shape, for example.

The entire width (width including both arms of the bifurcated shape) ofthe second bonding portion 20 b of the second metal terminal 16 b ispreferably not less than about 2.3 mm and not more than about 2.7 mm,for example.

The first extending portion 22 a of the first metal terminal 16 a isconnected to the first bonding portion 20 a and extends in the directionparallel or substantially parallel to the first main surface 12 a of theelement 12 with the space t1 from the first main surface 12 a. In thismanner, the first extending portion 22 a is disposed with the space t1from the first main surface 12 a, wherein a flow path of the exteriormaterial 18 is provided, and withstand voltage performance and moistureresistance performance are improved.

The width of the first extending portion 22 a of the first metalterminal 16 a is preferably not less than about 0.5 mm and not more thanabout 2.7 mm, for example. The length of the first extending portion 22a is preferably not less than about 1.8 mm and not more than about 2.2mm, for example.

In a portion of the first extending portion 22 a, a surface thereof ispreferably structured into a concave shape, and the parent material ofthe first metal terminal 16 a may be exposed at the processed portion.Consequently, even if the solder 40 in the first bonding portion 20 a,for example, solder melts, since the wettability of the solder decreasesdue to exposure of the parent material of the first metal terminal 16 aat the concave-shaped processed portion, flowing out of the solder isblocked, so that flowing of the melting solder to the outside of theexterior material 18 is effectively reduced or prevented.

The fifth extending portion 22 b of the second metal terminal 16 b isconnected to the second bonding portion 20 b and extends in thedirection parallel or substantially parallel to the second main surface12 b of the element 12 with the space t2 from the second main surface 12b. In this manner, the fifth extending portion 22 b is disposed with thespace t2 from the second main surface 12 b, wherein the flow path of theexterior material 18 is provided, and withstand voltage performance andmoisture resistance performance are improved.

The width of the fifth extending portion 22 b of the second metalterminal 16 b is preferably not less than about 1.5 mm and not more thanabout 2.7 mm, for example. The length of the fifth extending portion 22b is preferably not less than about 1.4 mm and not more than about 1.8mm, for example.

In a portion of the fifth extending portion 22 b, its surface ispreferably structured into a concave shape to provide a processedportion, and the parent material of the second metal terminal 16 b maybe exposed at the processed portion. Consequently, even if the solder 40in the second bonding portion 20 b melts, since the wettability of thesolder decreases due to exposure of the parent material of the secondmetal terminal 16 b at the concave-shaped processed portion, flowing outof the solder is blocked, so that flowing of the melting solder to theoutside of the exterior material 18 is reduced or prevented.

The second extending portion 24 a of the first metal terminal 16 a isconnected to the first extending portion 22 a and extends toward theelement 12. Specifically, the second extending portion 24 a is curvedfrom a terminal end of the first extending portion 22 a and extends to acentral portion of the element. For example, the curved portion may begently curved, or may be curved such that the angle of the curvedportion is substantially a right angle.

The width of the second extending portion 24 a of the first metalterminal 16 a is preferably not less than about 2.3 mm and not more thanabout 2.7 mm, for example. The length of the second extending portion 24a is preferably not less than about 0.6 mm and not more than about 1.0mm, for example.

The sixth extending portion 24 b of the second metal terminal 16 b isconnected to the fifth extending portion 22 b and extends toward theelement 12. Specifically, the sixth extending portion 24 b is curvedfrom a terminal end of the fifth extending portion 22 b and extends tothe central portion of the element. For example, the curved portion maybe gently curved, or may be curved such that the angle of the curvedportion is substantially a right angle.

The width of the sixth extending portion 24 b of the second metalterminal 16 b is preferably not less than about 2.3 mm and not more thanabout 2.7 mm, for example. The length of the sixth extending portion 24b is preferably not less than about 0.6 mm and not more than about 1.0mm, for example.

The third extending portion 26 a of the first metal terminal 16 a isconnected to the second extending portion 24 a and extends in thedirection parallel or substantially parallel to the first main surface12 a of the element 12. Specifically, the third extending portion 26 ais curved from a terminal end of the second extending portion 24 a andextends in the direction parallel or substantially parallel to the firstmain surface 12 a. For example, the curved portion may be gently curved,or may be curved such that the angle of the curved portion issubstantially a right angle.

The width of the third extending portion 26 a of the first metalterminal 16 a is preferably not less than about 2.3 mm and not more thanabout 2.7 mm, for example. The length of the third extending portion 26a is preferably not less than about 1.0 mm and not more than about 1.4mm, for example.

The seventh extending portion 26 b of the second metal terminal 16 b isconnected to the sixth extending portion 24 b and extends in thedirection parallel or substantially parallel to the second main surface12 b of the element 12. Specifically, the seventh extending portion 26 bis curved from a terminal end of the sixth extending portion 24 b andextends in the direction parallel or substantially parallel to thesecond main surface 12 b. For example, the curved portion may be gentlycurved, or may be curved such that the angle of the curved portion issubstantially a right angle.

The width of the seventh extending portion 26 b of the second metalterminal 16 b is preferably not less than about 2.3 mm and not more thanabout 2.7 mm, for example. The length of the seventh extending portion26 b is preferably not less than about 1.0 mm and not more than about1.4 mm, for example.

The fourth extending portion 28 a of the first metal terminal 16 a isconnected to the third extending portion 26 a and extends in themounting direction. Specifically, the fourth extending portion 28 a iscurved from a terminal end of the third extending portion 26 a andextends in a direction of the mounting surface. For example, the curvedportion may be gently curved, or may be curved such that the angle ofthe curved portion is substantially a right angle.

The width of the fourth extending portion 28 a of the first metalterminal 16 a is preferably not less than about 2.3 mm and not more thanabout 2.7 mm, for example. The length of the fourth extending portion 28a is preferably not less than about 1.0 mm and not more than about 1.4mm, for example.

The eighth extending portion 28 b of the second metal terminal 16 b isconnected to the seventh extending portion 26 b and extends in themounting direction. Specifically, the eighth extending portion 28 b iscurved from a terminal end of the seventh extending portion 26 b andextends in the direction of the mounting surface. For example, thecurved portion may be gently curved, or may be curved such that theangle of the curved portion is substantially a right angle.

The width of the eighth extending portion 28 b of the second metalterminal 16 b is preferably not less than about 2.3 mm and not more thanabout 2.7 mm, for example. The length of the eighth extending portion 28b is preferably not less than about 1.0 mm and not more than about 1.4mm, for example.

The first mounting portion 30 a of the first metal terminal 16 a is aportion connected to the fourth extending portion 28 a and mounted onthe mounting board. Specifically, the first mounting portion 30 a iscurved from a terminal end of the fourth extending portion 28 a andextends parallel or substantially parallel to the mounting surface. Agap portion 30 a 1 preferably having a rectangular or substantiallyrectangular shape is provided at a central portion of an end sideopposite to a side connected to the fourth extending portion 28 a of thefirst mounting portion 30 a. Two mounting pieces 30 a 2 and 30 a 3 arearranged at the end side opposite to the side connected to the fourthextending portion 28 a of the first mounting portion 30 a with the gapportion 30 a 1 provided between the mounting pieces 30 a 2 and 30 a 3.In this manner, since the end side opposite to the side connected to thefourth extending portion 28 a of the first mounting portion 30 a isbifurcated into the mounting pieces 30 a 2 and 30 a 3 by the gap portion30 a 1, even when the mounting piece 30 a 2 of the first mountingportion 30 a is deformed, the connection state is able to be maintainedby the mounting piece 30 a 3. Similarly, even when the mounting piece 30a 3 is deformed, the connection state is able to be maintained by themounting piece 30 a 2, so that mounting reliability is maintained.Accordingly, if the first mounting portion 30 a is deformed in a statein which the gap portion 30 a 1 is not provided, there is a possibilitythat mounting reliability cannot be ensured, such as, not being able tobe connected to the mounting board. In the first mounting portion 30 a,the gap portion 30 a 1 may not be provided.

As shown in FIG. 11, a plurality of small bending notches 30 a 4 and 30a 5 are provided at portions of both ends in a connecting portionbetween the first mounting portion 30 a and the fourth extending portion28.

This reduces physical resistance when the first mounting portion 30 a isbent, leading to a stable bending angle, and improved mountingreliability onto the mounting board is obtained.

In the first mounting portion 30 a, the bending notches 30 a 4 and 30 a5 may not be provided.

As shown in FIG. 12, it is preferable that the first mounting portion 30a is curved such that an extending angle β of the first mounting portion30 a is not less than about 0° and not more than about 10°, for example,with respect to the mounting surface (horizontal surface). Consequently,it is possible to include an appropriate amount of solder fillet whileensuring installation reliability for mounting with a mounter, thusimproving the mounting reliability.

The width of the first mounting portion 30 a of the first metal terminal16 a is preferably not less than about 2.3 mm and not more than about2.7 mm, for example. The length of the first mounting portion 30 a ispreferably not less than about 0.3 mm and not more than about 0.7 mm,for example.

The second mounting portion 30 b of the second metal terminal 16 b is aportion connected to the eighth extending portion 28 b and mounted onthe mounting board. Specifically, the second mounting portion 30 b iscurved from a terminal end of the eighth extending portion 28 b andextends parallel or substantially parallel to the mounting surface. Agap portion 30 b 1 preferably having a rectangular or substantiallyrectangular shape, for example, is provided at a central portion of anend side opposite to a side connected to the eighth extending portion 28b of the second mounting portion 30 b. Two mounting pieces 30 b 2 and 30b 3 are arranged at the end side opposite to the side connected to theeighth extending portion 28 b of the second mounting portion 30 b withthe gap portion 30 b 1 provided between the mounting pieces 30 b 2 and30 b 3. Since the end side opposite to the side connected to the eighthextending portion 28 b of the second mounting portion 30 b is bifurcatedinto the mounting pieces 30 b 2 and 30 b 3 by the gap portion 30 b 1,even when the mounting piece 30 b 2 of the second mounting portion 30 bis deformed, the connection state is able to be maintained by themounting piece 30 b 3. Similarly, even when the mounting piece 30 b 3 isdeformed, the connection state is able to be maintained by the mountingpiece 30 b 2, so that the mounting reliability is maintained.Accordingly, if the second mounting portion 30 b is deformed in a statein which the gap portion 30 b 1 is not provided, there is a possibilitythat the mounting reliability cannot be ensured, such as, not being ableto be connected to the mounting board. In the second mounting portion 30b, the gap portion 30 b 1 may not be provided.

A plurality of small bending notches 30 b 4 and 30 b 5 are provided atportions of both ends in a connecting portion between the secondmounting portion 30 b and the eighth extending portion 28 b. Thisreduces physical resistance when the second mounting portion 30 b isbent, leading to a stable bending angle, and the improved mountingreliability onto the mounting board is obtained. In the second mountingportion 30 b, the bending notches 30 b 4 and 30 b 5 may not be provided.

As in the first mounting portion 30 a, it is preferable that the secondmounting portion 30 b is curved such that the extending angle β of thesecond mounting portion 30 b is not less than about 0° and not more thanabout 10°, for example, with respect to the mounting surface (horizontalsurface). Consequently, it is possible to include an appropriate amountof solder fillet while ensuring installation reliability for mountingwith a mounter, thus improving the mounting reliability.

The width of the second mounting portion 30 b of the second metalterminal 16 b is preferably not less than about 2.3 mm and not more thanabout 2.7 mm, for example. The length of the second mounting portion 30b is preferably not less than about 0.3 mm and not more than about 0.7mm, for example.

It is preferable that the first metal terminal 16 a includes a firstcut-out portion 32 a in a portion in which the second extending portion24 a and the third extending portion 26 a of the first metal terminal 16a intersect with each other. As shown in FIG. 6, the first cut-outportion 32 a is covered with the exterior material 18. Although theshape of the first cut-out portion 32 a is not particularly limited, itis preferable that the first cut-out portion 32 a has a rectangular orsubstantially rectangular shape, for example. The width of the firstcut-out portion 32 a is preferably not less than about 0.4 mm and notmore than about 0.8 mm, for example. The length of the first cut-outportion 32 a is preferably not less than about 1.0 mm and not more thanabout 1.4 mm, for example.

It is preferable that the second metal terminal 16 b includes a secondcut-out portion 32 b in the fifth extending portion 22 b of the secondmetal terminal 16 b. As shown in FIG. 6, the second cut-out portion 32 bis covered with the exterior material 18. Although the shape of thesecond cut-out portion 32 b is not particularly limited, it ispreferable that the second cut-out portion 32 b has a circular orsubstantially circular shape, for example. As the size of the secondcut-out portion 32 b, the diameter is preferably not less than about 0.5mm and not more than about 1.5 mm, for example.

It is preferable that the second metal terminal 16 b includes a thirdcut-out portion 32 c in a portion in which the sixth extending portion24 b and the seventh extending portion 26 b of the second metal terminal16 b intersect with each other. As shown in FIG. 6, the third cut-outportion 32 c is covered with the exterior material 18. Although theshape of the third cut-out portion 32 c is not particularly limited, itis preferable that the third cut-out portion 32 c has a rectangular orsubstantially rectangular shape. The width of the third cut-out portion32 c is preferably not less than about 0.4 mm and not more than about0.8 mm, for example. The length of the third cut-out portion 32 c ispreferably not less than about 1.0 mm and not more than about 1.4 mm,for example.

The exterior material 18 is disposed to cover the element 12, the firstexternal electrode 14 a, the second external electrode 14 b, a portionof the first metal terminal 16 a, a portion of the second metal terminal16 b, a bonding portion between the first external electrode 14 a andthe first metal terminal 16 a, and a bonding portion between the secondexternal electrode 14 b and the second metal terminal 16 b.

The exterior material 18 preferably has a rectangular or substantiallyrectangular parallelepiped shape and includes a first main surface 18 aand a second main surface 18 b facing the first main surface 12 a andthe second main surface 12 b of the element 12, a first side surface 18c and a second side surface 18 d orthogonal to the first main surface 18a and the second main surface 18 b and extending in a length direction(a direction in which the metal terminal 16 extends), and a first endsurface 18 e and a second end surface 18 f orthogonal to the first mainsurface 18 a, the second main surface 18 b, the first side surface 18 c,and the second side surface 18 d. In the shape of the exterior material18, a central portion of the thickness direction (directions of thefirst main surface 18 a and the second main surface 18 b) may bestructured into a slightly convex shape along a circumferentialdirection. The shape of a corner portion of the exterior material is notparticularly limited, and the corner portion may be rounded, forexample. Specifically, it is preferable that the exterior material 18 ismolded in a tablet shape having a diameter of not less than about 10 mmand not more than about 20 mm, for example.

The first main surface 18 a and the second main surface 18 b of theexterior material 18 are preferably flat or substantially flat.

Preferably, the material of the exterior material 18 is, for example,formed by coating a resin, such as a liquid or powder silicone or epoxyresin. As the material of the exterior material 18, an engineeringplastic may be molded by an injection molding method, a transfer moldingmethod, or other suitable method.

In particular, the material of the exterior material 18 is preferablymade of a thermosetting epoxy resin, for example. Consequently, adhesionbetween the exterior material 18 and the element 12 or the metalterminal 16 is ensured, and improved withstand voltage and moistureresistance performance are obtained.

In the thickness of the exterior material 18, a thickness from a surfaceof the first external electrode 14 a of the element 12 to the first mainsurface 18 a of the exterior material 18 and a thickness from a surfaceof the second external electrode 14 b of the element 12 to the secondmain surface 18 b of the exterior material 18 are preferably not lessthan about 0.5 mm and not more than about 0.8 mm, for example. Further,a thickness from the side surface 12 c of the element 12 on the sideclosest to the first end surface 18 e of the exterior material 18 to thefirst end surface 18 e of the exterior material 18 and a thickness fromthe side surface 12 c of the element 12 on the side closest to thesecond end surface 18 f of the exterior material 18 to the second endsurface 18 f of the exterior material 18 are preferably not less thanabout 1.3 mm and not more than about 2.5 mm, for example. Furthermore, athickness from the side surface 12 c of the element 12 on the sideclosest to the first side surface 18 c of the exterior material 18 tothe first side surface 18 c of the exterior material 18 and a thicknessfrom the side surface 12 c of the element 12 on the side closest to thesecond side surface 18 d of the exterior material 18 to the second sidesurface 18 d of the exterior material 18 are preferably not less thanabout 0.2 mm and not more than about 1.4 mm, for example. Consequently,it is possible to secure required withstand voltage and reliabilitybetween the metal terminal 16 and the exterior material 18 whilemaintaining a small product size.

The first external electrode 14 a and the first metal terminal 16 a areconnected by the solder 40, and the second external electrode 14 b andthe second metal terminal 16 b are connected by the solder 40. Thesolder 40 is particularly preferably a lead-free solder having a highmelting point, for example.

The lead-free solder having a high melting point is preferably alead-free solder such as Sn—Sb based solder, Sn—Ag—Cu based solder,Sn—Cu based solder, or Sn—Bi based solder, and is more preferably aSn-10Sb to Sn-15Sb alloy solder, for example. The lead-free solderhaving a high melting point is more preferably a Sn-13Sb alloy solder,for example. Consequently, heat resistance of a bonding portion duringmounting is ensured.

As shown in FIG. 13, the solder 40 satisfies a relational expression“element diameter D (mm)×about 0.003 mm≤solder cross-sectional area S(mm²)≤element diameter D (mm)×about 0.02 mm”. This relational expressionis required to be satisfied with respect to both of the solder 40 forbonding the first external electrode 14 a and the first metal terminal16 a and the solder 40 to bond the second external electrode 14 b andthe second metal terminal 16 b. According to the verification result, aminimum value of a thickness of a peeling portion was about 0.02 mm. Ina case of “solder cross-sectional area S (mm²)>element diameter D(mm)×about 0.02 mm”, the solder volume exceeds the space size of thecross section, so that the solder reaches an electrode on the oppositeside through an element side surface, thus leading to short-circuiting.On the other hand, in a case of “element diameter D (mm)×about 0.003mm>solder cross-sectional area S (mm²)”, the thickness of the solder maybe less than the unevenness of the element, and portions which do notcome into close contact with each other are generated between the metalterminal 16 and the element 12, so that the bonding strength decreases.

From the viewpoint of bonding strength, it is preferable that therelational expression “solder cross-sectional area S (mm²)≤elementdiameter D (mm)×about 0.003 mm” is satisfied. Consequently, it ispossible to ensure bonding between the external electrode 14 and themetal terminal 16.

In a method of measuring the cross-sectional area of the solder, thecross-section polishing is performed on the surface mount electroniccomponent 10 including the metal terminals 16 to a position at which thewidth of the solder is largest, and the width and height of the solderare obtained from the cross section to calculate the cross-sectionalarea. For example, in a case of a shape of the second metal terminal 16b, as shown in FIG. 14, the surface mount electronic component 10 ispolished from the direction of the arrow A1, and the width and height ofthe solder at a position at which the area of the solder 40 is largest(a portion shown by a dashed line X1) are obtained to calculate thecross section. Alternatively, the surface mount electronic component 10is polished from the direction of the arrow A2, and the width and heightof the solder at a position at which the area of the solder 40 islargest (a portion shown by a dashed line X2) are obtained to calculatethe cross section.

Further, regarding the method of measuring the cross-sectional area ofthe solder, a complicated shape of the distal end of the first bondingportion 20 a of the first metal terminal 16 a, more specifically, aportion at which the distal end 20 a 2 is disposed in the direction awayfrom the first main surface 12 a as it approaches from the intermediateportion 20 a 1 of the first bonding portion 20 a towards the distal end20 a 2 and the intermediate portion 20 a 1 (that is, a portion locatedon the opposite side of the distal end of the first bonding portion 20a) of the first bonding portion 20 a is in surface contact with thefirst external electrode 14 a, is selected using a microscope, whereinthe area is calculated from the number of pixels. On this occasion, thecross-section polishing is performed at a position at which the solderwidth is largest at each bonding portion.

The dimension in the length direction of the surface mount electroniccomponent 10 (a direction in which the metal terminal extends) includingthe exterior material 18, the first metal terminal 16 a, and the secondmetal terminal 16 b is defined as the L dimension of the surface mountelectronic component 10, the dimension in the thickness direction of theexterior material (a direction connecting the first main surface 18 aand the second main surface 18 b of the exterior material 18) is definedas the T dimension of the surface mount electronic component 10, and thedimension in the width direction of the exterior material 18 (adirection connecting the first side surface 18 c and the second sidesurface 18 d of the exterior material 18) is defined as the W dimensionof the surface mount electronic component 10.

Although the dimensions of the surface mount electronic component 10 arenot particularly limited, preferably, the L dimension in the lengthdirection is not less than about 10.9 mm and not more than about 11.9mm, the W dimension in the width direction is not less than about 5.5 mmand not more than about 6.5 mm, and the T dimension in the thicknessdirection is not less than about 2.3 mm and not more than about 2.5 mm,for example.

Next, a preferred embodiment of a method of manufacturing a surfacemount electronic component having the above configuration will bedescribed by taking the surface mount electronic component 10 as anexample.

First, raw materials for manufacturing the element are provided andweighed.

Then, cobblestone is added to the raw material to be mixed and ground,and thus to be stirred, wherein the raw material is prepared.

Then, the prepared raw material is dried with a spray drier or othersuitable drier.

Subsequently, an additive, a binder or other suitable material is addedto the raw material to prepare a two-component raw material, and thetwo-component raw material is finely pulverized and then calcined.

Then, the calcined raw material is molded into a sheet shape by using anextruder or other suitable device.

Then, the sheet, which has been molded into a sheet shape, is punchedinto a disk tablet shape by using a press molding machine or othersuitable machine. Then, the sheet punched into a disk shape is filledinto a firing sagger, firing is performed, and the element 12 having adisk shape is manufactured. Although the firing temperature depends on adielectric material, it is preferably not less than about 1100° C. andnot more than about 1400° C., for example.

Then, the fired element 12 is set in a dry plating apparatus having avacuum chamber, and the pressure is reduced.

Then, the element 12 in the reduced pressure atmosphere is preheated ata temperature of not less than about 50° C. and not more than about 150°C., for example. At this time, since the element is preheated in a stateof being set in a reduced pressure atmosphere having an atmosphericpressure of about 0.5 torr, even when the heating temperature is as lowas not less than about 50° C. and not more than about 150° C., foreignmatters such as moisture adhered to the element 12 are able to beremoved efficiently.

Subsequently, when the preheating is completed, the interior of thevacuum chamber is evacuated again with a vacuum pump.

Then, the external electrodes 14 are formed on both main surfaces of theelement 12 by a dry plating method, such as vacuum vapor deposition,sputtering, ion plating, or plasma spraying in a state in which theatmospheric pressure in the vacuum chamber is stabilized at not lessthan about 10⁻⁶ torr and not more than about 10⁻³ torr, for example.

The first metal terminal 16 a and the second metal terminal 16 b areprepared. The first metal terminal 16 a and the second metal terminal 16b are molded by bending. The first cut-out portion 32 a formed in thefirst metal terminal 16 a and the second cut-out portion 32 b and thethird cut-out portion 32 c formed in the second metal terminal 16 b areformed by punching.

First, the solder 40 is applied onto an upper surface of the secondbonding portion 20 b of the second metal terminal 16 b (a surface facingthe second main surface 12 b of the element 12).

Then, the element 12 on which the external electrode 14 is formed isinserted between the first metal terminal 16 a and the second metalterminal 16 b.

Subsequently, the solder 40 is applied onto a contact surface betweenthe first metal terminal 16 a and the element 12.

Then, soldering is performed by reflow. As the soldering temperature, aheat of, for example, not less than about 270° C. and not more thanabout 300° C., for example, is preferably applied in reflow for not lessthan about 20 seconds.

Subsequently, in order to remove flux components included in the solder,ultrasonic cleaning using a solvent is performed. This is because if theflux remains attached, the adhesion between the exterior material 18 andthe element 12 decreases, which causes a decrease in withstand voltageand moisture resistance performance.

Next, the exterior material 18 will be described. As the exteriormaterial 18, an epoxy resin or other suitable material excellent inmoisture resistance is used.

Then, the metal terminal 16 after flux cleaning treatment is fixed in atransfer mold die which has been preheated to a range of not less thanabout 170° C. and not more than about 190° C., for example.

Subsequently, a tablet-shaped epoxy resin is pressed into the die by aplunger at a pressure of not less than about 10 MPa and not more thanabout 20, for example, for about 60 seconds to form the exteriormaterial 18 as shown in FIG. 1.

Then, after the exterior material 18 is formed, the metal terminal 16protruding from the exterior material 18 is bent along the side surfaceand the bottom surface of the exterior material 18 to obtain the surfacemount electronic component 10 shown in FIG. 1.

In the surface mount electronic component 10 shown in FIG. 1, theelement 12 on which the external electrode 14 is disposed is supportednot by a lead wire but by the metal terminal 16 and is able to bemounted on the mounting board by the metal terminal 16, and therefore,mounting by reflow is made possible.

Further, in the surface mount electronic component 10 shown in FIG. 1,the first metal terminal 16 a includes the first bonding portion 20 aconnected to the first external electrode 14 a, the first extendingportion 22 a connected to the first bonding portion 20 a and extendingin the direction parallel substantially parallel to the first mainsurface 12 a with a space t1 from the first main surface 12 a, thesecond extending portion 24 a connected to the first extending portion22 a and extending towards the element 12, the third extending portion26 a connected to the second extending portion 24 a and extending in thedirection parallel or substantially parallel to the first main surface12 a, the fourth extending portion 28 a connected to the third extendingportion 26 a and extending in the mounting direction, and the firstmounting portion 30 a connected to the fourth extending portion 28 a andmounted on the mounting board. In addition, the second metal terminal 16b includes the second bonding portion 20 b connected to the secondexternal electrode 14 b, the fifth extending portion 22 b connected tothe second bonding portion 20 b and extending in the direction parallelor substantially parallel to the second main surface 12 b with a spacet2 from the second main surface 12 b, the sixth extending portion 24 bconnected to the fifth extending portion 22 b and extending towards theelement 12, the seventh extending portion 26 b connected to the sixthextending portion 24 b and extending again in the direction parallel orsubstantially parallel to the second main surface 12 b, the eighthextending portion 28 b connected to the seventh extending portion 26 band extending in the mounting direction, and the second mounting portion30 b connected to the eighth extending portion 28 b and mounted on themounting board.

With the above-described configuration, the case member as disclosed inJapanese Patent Application Laid-Open No. 2007-81250 is not required,and the shape of the metal terminal 16 is optimized, so that an increasein the height dimension of the surface mount electronic component 10 isprevented, and the height of the surface mount electronic component 10is reduced.

Further, in the surface mount electronic component 10 shown in FIG. 1,the solder 40 is satisfied by the relational expression “elementdiameter D (mm)×about 0.003 mm≤solder cross-sectional area S(mm²)≤element diameter D (mm)×about 0.02 mm”. This relational expressionis satisfied with respect to both of the solder 40 for bonding the firstexternal electrode 14 a and the first metal terminal 16 a and the solder40 for bonding the second external electrode 14 b and the second metalterminal 16 b. Thus, since the solder amount is set within anappropriate range, even if the solder melts or expands when the surfacemount electronic component 10 is reflow-mounted on the mounting board,flowing of the solder between the covering member (coating portion,coating material) and the element 12 is reduced or prevented whilebonding is ensured, so that short-circuiting is prevented.

Further, with the surface mount electronic component 10 shown in FIG. 1,the first external electrode 14 a and the first metal terminal 16 a areconnected by the solder 40, and the second external electrode 14 b andthe second metal terminal 16 b are connected by the solder 40. When thesolder 40 is a lead-free solder having a high melting point, whilebonding strength between the element 12 and the metal terminal 16 isensured, heat resistance of the bonding portion to a flow or reflowtemperature during mounting of the board is ensured.

Further, in the surface mount electronic component 10 shown in FIG. 1,if the first main surface 18 a and the second main surface 18 b of theexterior material 18 are flat or substantially flat, sufficient flatnessis ensured. Thus, it is possible to prevent suction failure of a mounterof a mounting machine used to mount the surface mount electroniccomponent on the mounting board, and to reliably mount the surface mountelectronic component on the mounting board. As a result, occurrences ofmounting failure are effectively prevented.

Further, in the surface mount electronic component 10 shown in FIG. 1,the distal end 20 a 2 of the first bonding portion 20 a of the firstmetal terminal 16 a is disposed in the direction away from the firstmain surface 12 a from the intermediate portion 20 a 1 of the firstbonding portion 20 a towards the distal end 20 a 2, and the intermediateportion 20 a 1 (that is, a portion located on the opposite side of thedistal end of the first bonding portion 20 a) of the first bondingportion 20 a is in surface contact with the first external electrode 14a. Therefore, the amount of solder 40 that intrudes between the firstbonding portion 20 a and the first external electrode 14 a is increased.Therefore, the solder 40 can be sufficiently disposed between the uppersurface of the first external electrode 14 a and the first bondingportion 20 a of the first metal terminal 16 a, and the bonding strengthis increased.

In addition, the second bonding portion 20 b of the second metalterminal 16 b preferably includes a bifurcated (for example,wrench-shaped) distal end, and since the second bonding portion 20 b isin surface contact with the second external electrode 14 b at thebifurcated portion, the contact area between the second metal terminal16 b and the second external electrode 14 b is increased, so that theelement 12 is stably supported with good posture by the second externalelectrode 14 b, and the bonding strength is increased.

Further, in the surface mount electronic component 10 shown in FIG. 1,the first metal terminal 16 a includes the first cut-out portion 32 a inthe portion in which the second extending portion 24 a and the thirdextending portion 26 a of the first metal terminal 16 a intersect witheach other. Since the first cut-out portion 32 a is covered with theexterior material 18, the flow path of the exterior material 18 isprovided when the exterior material 18 is molded by injection molding,transfer molding, or other suitable method, and the filling property ofthe exterior material 18 is improved, so that improved withstand voltageperformance, moisture resistance reliability, and other characteristicsare obtained.

In addition, the second metal terminal 16 b includes the second cut-outportion 32 b in the fifth extending portion 22 b of the second metalterminal 16 b, and the second cut-out portion 32 b is covered with theexterior material 18. The second metal terminal 16 b further includesthe third cut-out portion 32 c in the portion in which the sixthextending portion 24 b and the seventh extending portion 26 b of thesecond metal terminal 16 b intersect with each other, and the thirdcut-out portion 32 c is covered with the exterior material 18.Therefore, a flow path of the exterior material 18 is provided when theexterior material 18 is molded by injection molding, transfer molding,or other suitable method, and the filling property of the exteriormaterial 18 is improved, so that improved withstand voltage performance,moisture resistance reliability, and other characteristics are obtained.

With the surface mount electronic component 10 shown in FIG. 1, when theexternal electrode 14 includes the Ni—Ti alloy layer made of a Ni—Tialloy and the Cu layer made of Cu and disposed on the surface of theNi—Ti alloy layer, improved bonding strength between the element 12 andthe Cu layer by the Ni—Ti alloy layer in the external electrode 14 isobtained, and improved electroconductivity and improved bonding strengthbetween the Cu layer and the solder by the Cu layer are obtained.

With the surface mount electronic component 10 shown in FIG. 1, when theexterior material 18 is made of a thermosetting epoxy resin, theadhesion between the exterior material 18 and the element 12 or themetal terminal 16 is ensured, and improved withstand voltage andmoisture resistance performance are obtained.

With the surface mount electronic component 10 shown in FIG. 1, theelement 12 preferably has a disk shape, and when the diameter of theelement 12 is not less than about 0.3 mm and not more than about 6.0 mm,and the thickness of the element 12 is not less than about 0.8 mm andnot more than about 1.2 mm, since the shape of the element 12 isoptimized, the size and height of the surface mount electronic component10 are reduced.

Next, in accordance with the manufacturing method described above, asurface mount electronic component was manufactured, and experimentswere conducted to confirm a short-circuit failure rate and a bondingstrength failure rate. For the experiments, samples Nos. 1 to 6 in whichthe amounts of solder bonding the external electrode and the metalterminal were made different were provided. The number of samples foreach sample number was set to 10 samples.

First, in order to produce the samples for each sample number, a surfacemount electronic component having the following specifications wasmanufactured in accordance with the above-described method ofmanufacturing a surface mount electronic component.

Diameter of element: D value: about 3.4 mm

Thickness of element: about 0.95 mm

Material of element: BaTiO₃

Capacitance: about 330 μF

Rated voltage: about 300 V

Structure of external electrode: four-layer structure

-   -   Material of first electrode layer (first layer): Ni—Ti alloy    -   Material of second electrode layer (second layer): Cu    -   Material of first electrode layer (third layer): Ni—Ti alloy    -   Material of second electrode layer (fourth layer): Cu    -   Thickness of first electrode layer (first layer): about 0.2 μm    -   Thickness of second electrode layer (second layer): about 0.3 μm    -   Thickness of third electrode layer (third layer): about 0.2 μm    -   Thickness of fourth electrode layer (fourth layer): about 0.2 μm

Structure of metal terminal

-   -   Shape: as shown in FIGS. 5 and 6    -   Material of terminal body (parent material) of metal terminal:        SUS alloy    -   Plating film: Two-layer structure of Ni plating film (first        layer) and Sn plating film (second layer)

Exterior material

-   -   Material: Epoxy resin

Solder

-   -   Material: Sn-13 Sb alloy    -   For a solder area, see Table 1.

A method of measuring the solder area was as follows. The soldercross-sectional area S was measured by extracting the solder area with amicroscope. At this time, cross-section polishing was performed to aposition at which the solder width was largest in both the solderconnecting the first external electrode and the first metal terminal andthe solder connecting the second external electrode and the second metalterminal.

A method of confirming short-circuit failure was as follows. First, eachsample was mounted on a glass epoxy substrate by using LF solder.Thereafter, a terminal of an IR meter (manufactured by HIOKI E.E.Corporation) was applied between the first electrode layer of theelement and the second electrode layer of the element from the firstmetal terminal and the second metal terminal, and a sample of not morethan about 1 GΩ, was judged as a sample in which short-circuit failureoccurred.

A method of confirming bonding strength failure was as follows. First,regarding the bonding strength, both side terminals were pulled in thevertical direction so as to move away from an element surface, andbreaking strength at that time was measured. The pulling speed was about10 mm/min. A breaking strength of not less than about 5N was judged asgood, and a breaking strength of less than about 5N was judged as bad.

Table 1 shows experimental results of the confirmation of short-circuitfailure and the confirmation of bonding strength failure.

TABLE 1 Solder cross- Solder cross- sectional Short- Bonding sectionalarea S/element circuit strength area S diameter D failure rate failurerate (mm²) (mm) (%) (%) Sample No. 1 0.0034 0.001 0 30 Sample No. 20.0102 0.003 0 0 Sample No. 3 0.034 0.01 0 0 Sample No. 4 0.068 0.02 0 0Sample No. 5 0.102 0.03 10 0 Sample No. 6 0.17 0.05 20 0

In the samples Nos. 2 to 4, the solder amount is set to satisfy therelational expression: element diameter D (mm)×about 0.003 mm≤soldercross-sectional area S (mm²)≤element diameter D (mm)×about 0.02 mm.Accordingly, no short-circuit failure occurred, and no bonding strengthfailure occurred.

According to the above experimental results, the minimum value of thethickness of the peeling portion of the terminal and the element wasabout 0.02 mm. In the samples Nos. 5 and 6, there was a sample in whichthe short-circuit failure occurred. The reason for this is consideredthat in the samples Nos. 5 and 6, since the relational expression“solder cross-sectional area S (mm²)>element diameter D (mm)×about 0.02mm” was satisfied, the solder volume exceeded the space size of thecross section, so that the solder reached an electrode on the oppositeside through an element side surface, thus leading to short-circuiting.

On the other hand, in the sample No. 1, there was a sample having poorbonding strength. The reason for this is considered that in the sampleNo. 1, since the relational expression “element diameter D (mm)×about0.003 mm>solder cross-sectional area S (mm²)” was satisfied, thethickness of the solder might be less than the unevenness of theelement, and portions which did not come into close contact with eachother were generated between the metal terminal and the element, so thatthe bonding strength decreased.

While preferred embodiments of the present invention have been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing from the scopeand spirit of the present invention. The scope of the present invention,therefore, is to be determined solely by the following claims.

What is claimed is:
 1. A surface mount electronic component comprising:an element including a dielectric layer including a first main surfaceand a second main surface; a first external electrode disposed on thefirst main surface; a second external electrode disposed on the secondmain surface; a first metal terminal connected to the first externalelectrode by solder; a second metal terminal connected to the secondexternal electrode by the solder; and an exterior material covering atleast a portion of the element, the first and second externalelectrodes, and the first and second metal terminals; wherein the firstmetal terminal includes: a first bonding portion connected to the firstexternal electrode; a first extending portion connected to the firstbonding portion and extending in a direction parallel or substantiallyparallel to the first main surface with a space from the first mainsurface; a second extending portion connected to the first extendingportion and extending towards the element; a third extending portionconnected to the second extending portion and extending in the directionparallel or substantially parallel to the first main surface; a fourthextending portion connected to the third extending portion and extendingin a mounting direction; and a first mounting portion connected to thefourth extending portion and mounted on a mounting board; the secondmetal terminal includes: a second bonding portion connected to thesecond external electrode; a fifth extending portion connected to thesecond bonding portion and extending in a direction parallel orsubstantially parallel to the second main surface with a space from thesecond main surface; a sixth extending portion connected to the fifthextending portion and extending towards the element; a seventh extendingportion connected to the sixth extending portion and extending in thedirection parallel or substantially parallel to the second main surface;an eighth extending portion connected to the seventh extending portionand extending in the mounting direction; and a second mounting portionconnected to the eighth extending portion and mounted on the mountingboard; and the solder satisfies a relational expression: elementdiameter D (mm)×about 0.003 mm≤solder cross-sectional area S(mm²)≤element diameter D (mm)×about 0.02 mm.
 2. The surface mountelectronic component according to claim 1, wherein the solder is alead-free solder having a high melting point.
 3. The surface mountelectronic component according to claim 1, wherein upper and lowersurfaces of the exterior material are flat or substantially flat; in thefirst bonding portion, a distal end of the first bonding portion isdisposed in a direction away from the first main surface from anintermediate portion of the first bonding portion towards the distalend, the first bonding portion is in surface contact with the firstexternal electrode at the intermediate portion located on an oppositeside of the distal end; a first cut-out portion is provided in a portionin which the second extending portion of the first metal terminal andthe third extending portion of the first metal terminal intersect witheach other; the second bonding portion includes a bifurcated distal endand is in surface contact with the second external electrode at thebifurcated portion; a second cut-out portion is provided in the fifthextending portion of the second metal terminal; a third cut-out portionis provided in a portion in which the sixth extending portion of thesecond metal terminal and the seventh extending portion of the secondmetal terminal intersect with each other; and the first, second, andthird cut-out portions are covered with the exterior material.
 4. Thesurface mount electronic component according to claim 1, wherein each ofthe first external electrode and the second external electrode includesa first electrode layer made of a Ni—Ti alloy and a second electrodelayer made of Cu.
 5. The surface mount electronic component according toclaim 1, wherein the exterior material is made of a thermosetting epoxyresin.
 6. The surface mount electronic component according to claim 1,wherein the element has a disk shape; a diameter of an outer shape ofthe element is not less than about 3.4 mm and not more than about 5.0mm; and a thickness t of the element is not less than about 0.90 mm andnot more than about 0.95 mm.
 7. The surface mount electronic componentaccording to claim 1, wherein the element is a single ceramic plate. 8.The surface mount electronic component according to claim 1, wherein theelement is made of a dielectric ceramic primarily including at least oneof BaTiO₃, CaTiO₃, SrTiO₃, and CaZrO₃.
 9. The surface mount electroniccomponent according to claim 1, wherein the element is a capacitor. 10.The surface mount electronic component according to claim 1, wherein theelement has a disk shape; a diameter of an outer shape of the element isnot less than about 3.0 mm and not more than about 6.0 mm; and athickness t of the element is not less than about 0.80 mm and not morethan about 1.2 mm.
 11. The surface mount electronic component accordingto claim 1, wherein each of the first and second external electrodes ismade of at least one of Cu, Ni, Cr, Ag, Pd, Au, Ti, Ag—Pd alloy, Cu—Nialloy, Cu—Ti alloy, Ni—Cr alloy, and Ni—Ti alloy.
 12. The surface mountelectronic component according to claim 4, wherein each of the firstexternal electrode and the second external electrode includes two of thefirst electrode layers and two of the second electrode layers that arealternately arranged.
 13. The surface mount electronic componentaccording to claim 4, wherein a thickness of each of the first andsecond electrode layers is not less than about 0.1 μm and not more thanabout 0.35 μm.
 14. The surface mount electronic component according toclaim 1, wherein a thickness of each of the first and second externalelectrodes is not less than about 0.7 μm and not more than about 1.2 μm.15. The surface mount electronic component according to claim 1, whereineach of the first and second metal terminals includes a terminal bodyand a plating film provided on a surface of the terminal body.
 16. Thesurface mount electronic component according to claim 15, wherein theterminal body is made of Ni, Fe, Cu, Ag, Cr, or an alloy primarilyincluding one or more of Ni, Fe, Cu, Ag, and Cr.
 17. The surface mountelectronic component according to claim 15, wherein a thickness of theterminal body is not less than about 0.05 mm and not more than about 0.5mm.
 18. The surface mount electronic component according to claim 15,wherein the plating film includes a lower plating film provided on asurface of the terminal body and an upper plating film provided on asurface of the lower plating film.
 19. The surface mount electroniccomponent according to claim 18, wherein the lower layer plating film ismade of Ni, Fe, Cu, Ag, Cr, or an alloy primarily including one or moreof Ni, Fe, Cu, Ag, and Cr.
 20. The surface mount electronic componentaccording to claim 18, wherein the upper layer plating film is made ofSn, Ag, Au, or an alloy primarily including one or more of Sn, Ag, andAu.